This project represents a continuing effort to develop the acellular slime mold Physarum polycephalum as a model system for biochemical, genetic, ultrastructural, and phenomenological studies of the molecular bases of a wide variety of eukaryotic cell movements. During the next fiscal year of the project several specific goals will be pursued. A major effort will be directed at completing the physico-chemical and functional characterization of plasmodial and microplasmodial actins particularly with regard to clarifying mechanisms which might regulate the in vivo assembly and disassembly of actin polymers. Final modifications in the myosin isolation protocol will allow characterization of the enzyme with special emphasis on its interaction with actin. Also projected is the completion of the development of those genetic techniques needed for analysis of mutants in amoebal colony morphology, amoeboid motility, and amoebo-flagellate transformation. Analyses of amoebal motility will continue including studies of the effects of pH and bacterial substratum on colony form in wild type cells and the effect of cell distribution and substratum pH on the orientation and rate of movement of individual cells. Studies of the amoebo-flagellate transformation will include isolation and characterization of actin, myosin, tubulin, and dynein; electron microscopic examination of cells at various stages of the transformation; comparison of wild type cells with several mutants available as regards potential for transformation, temperature dependence of the transformation process, and behavior of the resulting myxoflagellates; and isolation of further mutants involving not only the ability to achieve the potential for transformation but also involving processes occurring during the transformation.